Think you're on the Internet right now? Well, you're not. You're on your Internet. The exact version of the online world that you see is available only to you.

Most of the major conduits through which you see the world online, including Google Search and Facebook, are gathering all kinds of data about you, then presenting you with a custom version of the world they think you're interested in. They're hiding or de-emphasizing the version of the world they assume you're not interested in.

In the past two years, the biggest gatekeeper websites have gotten very good at figuring out what you want and giving it to you. What's wrong with that?

There are downsides, according to a new book called The Filter Bubble: What the Internet Is Hiding From You.

In a nutshell, the book argues that the sophisticated personalization engines improve things in the short run. But in the long run, they dumb us down, reduce our exposure to new ideas and ultimately could lead to a society without a shared set of facts about the world. The personalized Internet favors the marketers and propagandists but provides an obstacle for people who are trying to introduce new ideas.

The Internet is increasingly turning us all into dictators and divas. Like the entourages of Saddam Hussein or Jennifer Lopez, the Internet tells us what we want to hear, feeding us a version of the world that feels good, goes down easy and doesn't challenge us.

The book ships May 16. It was written by Eli Pariser, who is the president of the MoveOn.org board. MoveOn is a liberal public-policy group, and Pariser's concerns are mainly political. But the "filter bubble" concept affects you no matter what your interests. And you're going to hear a lot about this concept after the book hits.

In this column, I'm going to tell you how personalization works, why you may not want it, and also how to pop the bubble and opt out of a system that censors your Internet based on stereotyping.

Your own private Google

The "secret sauce" of Google Search has long been an algorithm called PageRank (named after co-founder Larry Page). But on Dec. 4, 2009, Google announced an additional algorithm that custom-tailors search results according to the individual attributes of the user.

According to Pariser, Google uses 57 "signals" -- even when you're not logged in to Google -- to customize search results. (Google was unable to confirm the number of signals.)

These "signals" include where you are, what you have clicked on in the past and who your friends are. But that's just the beginning. Google also gathers information about which browser and device type you use, how much you travel (based on where you use search over time), how long it takes you to click after getting a search result, and many, many other data points.

From all this data, Google decides how to sort your search results. (A Google spokesman told me the company rejects the term "filter" because it implies that Google is hiding links rather than prioritizing them.)

Here's a fun experiment to try. Search for something on Google, and have a friend or two do the same search. See how the results are different? Many of the links are the same. But they're in a different order and "skewed" subtly in one direction or another.

As we increasingly use mobile devices, our exact locations, where we've been, which stores and restaurants we've entered, who we've met with and possibly even activities on unrelated services will be increasingly factored into the decision-making process about what we see and don't see. In fact, all the major improvements Google has promised for search involve far more and deeper personalization.

"The power of individual targeting -- the technology will be so good, it will be very hard for people to watch or consume something that has not in some sense been tailored for them," according to Eric Schmidt, Google's executive chairman.

Google apparently tries to be responsible with its power over your attention. A spokesman told me Google understands that "people value diversity on results pages." The company uses its deep understanding of you not only to target your assumed interests, but also to deliberately challenge you with a few links outside those interests.

Facebook's antisocial filter

Facebook is less responsible, in my opinion. The social networking giant determines what appears in your "News Feed" using an algorithm called EdgeRank. (Facebook ignored my request for an interview.)

Every action you take on Facebook -- clicking "Like," commenting, sharing, etc. -- is called an "Edge" internally at Facebook. Each Edge is weighted differently according to secret criteria.

What you need to know is that relationships and content that don't get enough "Edges" will get "edged" out of existence. Facebook will cut your ties to people -- actually end the relationships you think you have -- and block content that doesn't earn enough Edge points.

For example, many Facebook friendships exist solely through reading each other's Status Updates. An old friend or co-worker talks about a new job, shares a personal triumph like reaching a weight-loss goal, and tells a story on Mother's Day about how great his mom is. He posts and you read. You feel connected to his life.

Any friends who fail to click or comment on your posts will stop getting your status updates, too. If you have 500 friends, your posts may be actually delivered to only 100 of them. There's no way for you to know who sees them and who doesn't.

Facebook also filters content. EdgeRank keeps track of how many of your friends comment on a link to content, and it will use that criteria in the default view of your News Feed, which is the "Top Stories" setting.

The vast majority of even technical, savvy people I asked about this have no idea that their friends' activities are determining what content they see and don't see on Facebook.